The present invention generally relates to front-tooth matrices and more particularly to a matrix band and a matrix retainer for disposable front-tooth matrices.
In odontology, dental matrices are used for shaping the outer contour of a filling so as to make it merge naturally into the adjoining surfaces of the prepared tooth.
The demand placed on a matrix band for such a matrix primarily is that it should ensure the making of a filling without any deficiency of material, i.e. where the filling does not reach as far as the natural contour of the tooth, but also prevent exaggerated excess of material, which has to be removed at a later stage. The matrix band should also permit light-curing, i.e. it must be translucent. Generally, it therefore consists of plastic.
One example of a known matrix is described in EP-A1-0 227 590 where a flat matrix band is combined with a retainer in the form of two wedges and a sleeve. The ends of the matrix band are inserted between the two wedges, which in turn are partially inserted in the sleeve. When a loop of the matrix band has been applied around a tooth, the sleeve is moved towards the tooth so as to clamp the wedges to each other and to the band ends within the sleeve, thus clamping the band around the tooth. This results however in unreliable fixation of the band, and this matrix is not suited at all for use on front teeth, since the flat band is unable in this case to satisfy the primary requirement as set out above. This is so, above all, because of the wedge shape of the front teeth with a partly concave palatal side and a convex buccal side.
Another example of a known matrix is described in WO85/01434 where preformed matrix sheeting is used. In view of the considerable variation in shape and size of the teeth in one individual and of the teeth in different individuals, such preformed matrix sheeting is no viable alternative.
Therefore, the commonest method in filling therapy on front teeth is as follows. A flat, flexible matrix band of transparent plastic is used and applied by the dentist in a loop around the tooth concerned. When the filling material has been applied, the dentist holds the band tightly against the tooth with two fingers in order to contour the filling while an assistant is illuminating the filling, for example with visible light, with a view to curing the filling by polymerization. Alternatively, the band is maintained in position for several minutes in order that the filling material should cure chemically. This mode of operation suffers from obvious drawbacks. Thus, it is possible to make only one filling at a time and the risk of excess or deficiency of material is considerable, since it is difficult to properly observe the filling site. This also entails a considerable risk of deficient polymerization in the event light is used for producing it.